dt-bindings: net: davicom,dm9000: convert to DT schema

Convert the Davicom DM9000 Fast Ethernet Controller bindings to DT
schema.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230713152848.82752-4-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>